Yelverton, Barry (1736–1805), 1st Viscount Avonmore , lawyer and MP, was born 28 May 1736 near Newmarket, Co. Cork, eldest son of Francis Yelverton (1705–46), of Blackwater, and his wife Elizabeth (d. 1804), daughter of Jonas Barry of Kilbrin, all of Co. Cork. Yelverton's family was protestant but far from affluent. He received his early education at Charleville (possibly with spells also at Newmarket and Midleton) before being admitted to TCD (1753) on a sizarship, which allowed him reduced fees. While at Trinity he was a founder of the Historical Club (1753). Sheer poverty compelled him to spend several humiliating years thereafter as usher in the Hibernian Academy run by Dr Andrew Buck in Dublin's North King St. Reportedly at the urging of his friends he put his name forward for the Middle Temple on 10 October 1759, and returned to TCD to take an LLB in 1761. In July of that year he married Mary Nugent (1733–1802), daughter of William Nugent of Clonlost, Co. Westmeath, whose comfortable financial circumstances allowed him to study for the Irish bar, to which he was called in 1764. A combination of ambition, rhetorical skills, and intellect brought him to the attention of the lord chancellor, James Hewitt (qv), later 1st Viscount Lifford, and he was appointed KC in 1772. In the same year he was made a bencher of the King's Inns. In 1774, his merit and abilities having been recognised by the conferring of an LLD, he left the law temporarily for politics.
Yelverton represented first the borough of Donegal under the patronage of Arthur Saunders Gore (‘commonly called’ Lord Sudley) in 1774, but in the general election two years later he was brought in for the county and town of Carrickfergus by Arthur Chichester (qv), 5th earl of Donegall (he was also returned for both Donegal and Belfast). Before long it became clear that Yelverton was ‘not entirely guided’ by his patrons (quoted in HIP, vi, 571). Led by his own beliefs and perhaps taking advantage of the ‘wavering disposition’ of his first patron, Gore, Yelverton adopted a Patriot stance, opposing the government during the earlier stages of the American war in 1775–6. On the other great issue of the day, the first substantial catholic relief measure in 1778, he was a prominent supporter of the bill. Having established a reputation as an articulate and courageous exponent of patriotic liberalism, Yelverton founded in 1779 a convivial, but essentially political, society formally entitled the Order of St Patrick but remembered ever after as ‘The Monks of the Screw’. He was its first ‘abbot’, with his old friend and Patriot colleague John Philpot Curran (qv) as ‘prior’. At the height of the free trade dispute of 1779–80 he was one of the instigators of the short (six-month) money bill which helped to keep the initiative in Irish parliamentary hands. Yelverton was an early member of the Irish Volunteers. By the end of 1779 he was regarded by the Irish administration at Dublin Castle as being a strong and decided factionist. In a loose association with Henry Grattan (qv) and other Patriots Yelverton began a campaign for the amendment of Poynings’ law of 1494 and the repeal of the British declaratory act of 1720, both of which were seen as unconstitutional restraints on the liberty of the Irish parliament. His motion of 26 April 1780, for leave to introduce a measure to abolish the power of the Irish privy council to alter and suppress Irish legislation, was defeated by a narrow majority.
The unstable character of Yelverton's political alliance with Grattan became clearer as each man pursued a separate strand of the eventual settlement of 1782, often without reference to the other. For Yelverton a crucial juncture was brought about by the news of the surrender of the British forces under Lord Cornwallis (qv) to the American rebels at Yorktown, Virginia, in the autumn of 1781. Despite Grattan's determination to oppose the loyal address considered by the government to be highly desirable at such a time of imperial crisis, Yelverton chose this moment to make a confidential arrangement with the chief secretary, William Eden (qv). Yelverton agreed to bring forward personally the loyal address on 4 December 1781. In return the government agreed to adopt a neutral stance when Yelverton proposed his amendment to Poynings’ law a few weeks later. As the government had hoped, Yelverton in moving the loyal address brought most of the house of commons with him, leaving Grattan relatively isolated. Two weeks later, on 18 December, Yelverton's introduction of his measure to amend Poynings’ law was carried unanimously. By the time the Irish parliament came to consider the substance of the measure in March 1782, the political circumstances consequent to the Yorktown defeat had fatally weakened the government's power to offer any effectual criticism. Yelverton's amendment, which bound the Irish privy council to pass Irish draft legislation to its counterpart in London ‘without addition, diminution or alteration’, became a corner-stone of the legislative independence enjoyed and staunchly defended by the Irish parliamentarians until the union of 1800.
But Yelverton's long flirtation with opposition politics had had its expensive side, and, despite his fortunate marriage, he was not a wealthy man. He accepted the post of attorney general under the lord lieutenancy of the duke of Portland (qv) in July 1782. His connection with the Volunteers ended, and the distance between him and Henry Flood (qv) increased when he rebuffed an attempt by Flood to introduce a parliamentary reform proposal in November 1783. Never a very worldly man, Yelverton a month later left mainstream politics for the post of chief baron of the exchequer. He was elected an MRIA in 1787. During the regency crisis of 1788–9 he adopted the apparently conservative stance that any action by the Irish parliament should wait on guidance from Westminster, but was yet supportive of the prince of Wales's right to succeed, a demonstration of the lifelong conflict within him between duty and principle. In 1795, despite the arrival in office of the whig Lord Fitzwilliam (qv), Yelverton was passed over for further advancement and instead was created Baron Avonmore. During the disturbances of the latter 1790s it fell to Yelverton to pass sentence of death on the United Irishman William Orr (qv); the judge was then observed to put his head in his hands and weep. His known hastiness in reaching decisions tarnished his judicial reputation, but his career revived somewhat after his spirited support of the act of union, on which he was created Viscount Avonmore. However, 1802 saw his failure to retake the attorney generalship, and also brought the death of his wife.
For most of his career Yelverton lived at Fortfield, Templeogue, Dublin, where he died on 19 August 1805, and was buried nearby at Rathfarnham. He had a daughter and three sons, one of whom, Walter Aglionby Yelverton (1772–1834), represented Tuam in the Irish parliament from 1797 until the union. Two portraits, both in oils, were executed. One, by Hugh Douglas Hamilton (qv), hangs in the King's Inns, Dublin; the other, a posthumous likeness by G. F. Joseph (1764–1846), is in TCD.